The present invention relates to a sealing device for a water pump bearing.
For example, a structure such as shown in FIG. 8 is known as a water pump for circulating cooling water in an automobile engine, or the like.
The water pump comprises a pump shaft 1, an impeller 2, a mechanical seal 3, a water pump bearing 4, sealing devices 5 and 6 for the water pump bearing, a pulley 7, etc. The impeller 2 is attached to one end of the pump shaft 1, and the pulley 7 is attached to the other end. The pump shaft 1 and the impeller 2 are rotated by a belt (a belt which transmits rotation of a crankshaft of an engine) which is wound around the pulley 7, so that cooling water in a pump chamber is sent out.
In the water pump bearing 4, the pump shaft 1 is used as an inner race, and an outer race 41 is externally attached to the outer peripheral face of the inner race via a cylindrical roller group 42 and a ball group 43 serving as rolling elements. The bearing 4 is disposed in a boss portion 10 of a pump housing.
The sealing device 5 which is disposed on the side of one end (on the side of the impeller) in the axial direction of the water pump bearing 4 performs a sealing action so that, even when the cooling water in the pump chamber leaks from the mechanical seal 3, the cooling water does not enter the interior of the water pump bearing 4, thereby allowing the leaking cooling water to be discharged to the outside through a drain hole 111 of the boss portion 10. The sealing device 5 is configured by an annular seal member 51 and an annular slinger 52.
The seal member 51 of the sealing device 5 is fixed to a shoulder portion of one end in the axial direction of the outer race 41, and, as enlargedly shown in FIG. 9, configured by integrally heat bonding an elastic member 51b in which two radial lips 51c and 51d, and one axial lip 51e are formed, and which is made of synthetic rubber or the like, to an annular core 51a. By contrast, the slinger 52 is positioned on the side of the one end (on the side of the impeller) in the axial direction with respect to the seal member 51, and externally fitted and fixed to the outer peripheral face of the pump shaft 1. The axial lip 51e of the seal member 51 is in contact with a disk portion 52a of the slinger 52. The two radial lips 51c and 51d of the seal member 51 are in contact with the outer peripheral face of the pump shaft 1.
In the sealing device 5 of the water pump bearing 4 which is on the side of the impeller, the seal performance is improved by using the seal member 51 of the triple lip type in which the two radial lips 51c and 51d and the one axial lip 51e are disposed. However, the seal member 51 of the triple lip type configured as described above has a complicated structure because it has the axial lip 51e, thereby producing a problem in that the cost is increased.
The invention has been conducted in order to solve the aforementioned problem. It is an object of the invention to provide a sealing device for a water pump bearing which can exhibit excellent seal performance although using an economical seal member of a simple structure having no axial lip.